Geometry Sensitivity of Magnetohydrodynamic Duct Flow and Some Abnormal Phenomena

Abstract

Geometry sensitivity of magnetohydrodynamics (MHD) duct flow and some abnormal phenomena deviating from the classical MHD laws were measured in an experimental investigation of the MHD effect of the flow channel inserter (FCI) duct flow. The results showed that the velocity distribution deviated from the M-type profile on the centre-plane of the cross section of the duct with small slots (in short "S-duct"). The electric potential difference in the duct wall was much lower than that given by the classical electromagnetic laws. The MHD pressure drop was much higher than that from the classical magneto-hydrodynamics theory. These results may help us find some new methods to reduce the MHD pressure drop, or explore other potential applications such as flow structure control.

Experimental Base of an Innovation S-Channel to Reduce MHD Pressure Drop

“…But we can understand why the peak is of difference in two cases (Pr-duct and Sv-duct cases). The diagram of the secondary flow due to the protruding twigs and slots (see Figure 7, and see ref [1]) can help to understand the difference of the velocity distribution. It can be seen that the secondary flow due to one pair of protruding twig in the Pr-duct, and that due to by two pair of slots in the Sv-duct.…”

“…Before we state the detail of the special design experiments, we review the MHD geometry sensibility phenomena (see [1,2]): A rectangular duct with two small weld slots, i.e., "Sc-duct", was fabricated with two simple Utype 304 stainless steel channels welded at the middle line of the lengthwise sides( designed to reduce the manufacture cost) while conducting experimental investigations on the MHD effect of the FCI flow. Yet, a dramatic influence on the flow pattern, pressure gradient and electric potential distribution had been measured [1]. It can be found that the small weld slots make the center velocity and the MHD pressure drop to increase, and the velocity distribution on the center-plane (y = 0) of the cross section of the duct deviates from the classical M-type profile.…”

“…As known, liquid metal blanket concepts are still attractive ITER (International Thermonuclear Experimental Reactor) and DEMO (Demonstration fusion plant) blanket candidates as they have low operating pressure, simplicity, and a convenient tritium breeding cycle. While conducting an experimental investigation of MHD effect of the flow channel inserts (FCI) for liquid metal blanket system in ITER or DEMO potential application, some MHD geometry sensibility phenomena were measured in accident case [1], and the MHD geometry sensibility phenomena (or called the secondary flow MHD effect, short in "S-MHD" effect) is successfully used to understand FCI duct flow MHD behaviors [2,3], and the experimenttal results of FCI flow indicate that the problem how to reduce the MHD pressure drop and meet the heat transferred requirement still remain key issues. As well as, up to now, it is very little about the secondary flow knowledge.…”